Twelve active chronic alcoholic subjects were enrolled in the CRC portion of the protocol during the last study year. Each subject was successfully monitored without medical intervention through withdrawal from alcohol. During the process of withdrawal, behavioral assessments were conducted three times a day, measuring the degree of craving for alcohol, the magnitude of withdrawal as well as other behaviors. On Day Four of the GCRC admission, patients underwent a PET imaging procedure to measure opioid receptor density in various regions of the central nervous system. On Day Five, the last day of admission, the patient's underwent a naloxone challenge test to ascertain functional assessment of endogenous opioid activity within the central nervous system. Study results indicate a significant positive correlation between craving for alcohol and opioid receptor density in key regions of the CNS.